Techniques herein relate to methods of fabricating semiconductors including methods for patterning substrates.
Fabricating semiconductors includes patterning a wafer surface to be able to create various trenches, holes, and openings in underlying layers. Currently there are challenges with using lithographic tools to create patterns having critical dimensions to meet design specifications. In other words, due to the resolution limitations of patterning photoresists, patterns developed from photoresists do not have lines, trenches, and holes that are sufficiently small to meet design specifications. One technique to shrink patterns to desired dimensions is known as directed self-assembly (DSA).
Directed Self-Assembly (DSA) is a block copolymer process that uses a manufactured polymer that consists of two blocks that are connected. With proper activation, the two (or more) block copolymers will micro phase separate into individual blocks. Conceptually this is similar to how oil can be attached to water via soap. Typically oil and water to not mix but can be held together with certain binding chemicals, but with these binding chemicals removed, oil and water will separate. Likewise, two different blocks in a block copolymer mixture will repel each other, while other blocks can be attracted to themselves. Activation is typically executed via heat energy which causes block copolymer separation on a nanoscale based on various polymer parameters. This phase separation causes nanometer-sized structures to be formed. Typically this is an alternating or repeating pattern of structures being formed. For example, alternating lines of block copolymer can be formed or assembled. Also, one block copolymer can form cylinders while the second block copolymer forms around the cylinders. Using DSA, cylindrical structures can be created based on Kai the Flory interaction parameter and N—the statistical molecular weight and the volume. When DSA is coupled with a photoresist pattern (or other pattern) sub-resolution structures can be formed. This is possible because multiple lines or cylinders can be formed within feature dimensions defined by a photoresist pattern. Accordingly, patterned dimensions provided by a photoresist pattern can be shrunk to various design specifications.